Ink ribbon units for use in printers are composed of a supply spool with a coil of unused ink ribbon wound thereon and a take-up spool for winding a used ink ribbon thereon. In use, an ink ribbon unit that is housed in an ink ribbon cassette is set in a printer, which then prints a desired image on a photographic sheet of paper using the ink ribbon unit. Ink ribbon units themselves are commercially available in the market.
If the supply and take-up spools of an ink ribbon unit were freely rotatable of their own accord, then the ink ribbon would tend to become loose, making the ink ribbon unit less commercially valuable. To prevent the ink ribbon from being loosened, it has been customary to incorporate some means for fastening and locking the supply and take-up spools against free rotation.
Several conventional mechanisms for fastening and locking supply and take-up spools against free rotation will hereinafter be described below with reference to the drawings.
In FIG. 1 of the accompanying drawings, an ink ribbon unit 10 comprises a supply spool 1 with an unused ink ribbon 2 wound thereon, and a take-up spool 3 which winds the ink ribbon that has been consumed which has been supplied from the supply spool 1. The supply and take-up spools 1, 3 have on one end thereof respective driving side shafts 6, 7 having respective flanges 4, 5 at proximal ends thereof. The driving side shafts 6, 7 have respective circular drive holes 6a, 7a defined axially therein and respective sets of drive teeth 6b, 7b on their inner circumferential surfaces. The circular drive holes 6a, 7a serve to receive therein respective drive shafts (not shown) in a printer that are connected to an actuator such as a motor. When the drive shafts are received in the circular drive holes 6a, 7a, drive teeth on the drive shafts mesh with the drive teeth 6b, 7b to transmit drive forces to the supply and take-up spools 1, 3. The supply and take-up spools 1, 3 also have respective rotary side shafts 8, 9 on the other end thereof.
The ink ribbon unit 10 shown in FIG. 1 may be housed in an ink ribbon cassette which, as shown in FIG. 2 of the accompanying drawings, comprises a lower casing 50 and an upper casing 51 which are combined with each other. The lower casing 50 is somewhat tray-shaped and has on one end thereof a pair of transversely spaced driving side shaft bearings 52 with respective circular bearing holes 52a defined therein. The driving side shafts 6, 7 of the ink ribbon unit 10 are rotatably disposed in the respective bearing holes 52a in the driving side shaft bearings 52. The lower casing 50 also has on its other end a pair of transversely spaced rotary side shaft bearings 53 with respective U-shaped bearing slots 53a defined therein. The rotary side shafts 8, 9 of the ink ribbon unit 10 are rotatably disposed in the respective bearing slots 53a in the rotary side shaft bearings 53. An opening 54 for positional alignment with a print head (not shown) is defined in the lower casing 50 between its opposite ends.
The upper casing 51 is combined with the end of the lower casing 50 which has the rotary side shaft bearings 53. The upper casing 51 has a pair of spaced leaf springs 55 aligned respectively with the rotary side shaft bearings 53 for holding the rotary side shafts 8, 9 that are received respectively in the bearing slots 53a.
The ink ribbon unit 10 itself may be sold in different ways as described below.
FIG. 3 of the accompanying drawings shows one form in which the ink ribbon unit 10 is offered for sale. In FIG. 3, an adhesive tape 11 is applied to the ends of the driving side shafts 6, 7 of the ink ribbon unit 10 to fasten and lock the supply and take-up spools 1, 3 against free rotation.
FIG. 4 of the accompanying drawings shows another form in which the ink ribbon unit 10 is offered for sale. In FIG. 4, a rubber band 12 is placed around the ink ribbon unit 10 to fasten and lock the supply and take-up spools 1, 3 against free rotation.
The ink ribbon unit 10 may be offered for sale in still another form shown in FIG. 5 of the accompanying drawings. In FIG. 5, the ink ribbon unit 10 is placed in a transparent package bag 13 made of plastic or the like, and the package bag 13 is folded over on itself and fastened by an adhesive tape 13a. The supply and take-up spools 1, 3 thus contained in the package bag 13 and secured by the adhesive tape 13a are fastened and locked against free rotation.
The form shown in FIG. 3 has been disadvantageous in that it is difficult to apply the adhesive tape 11 precisely to the ends of the driving side shafts 6, 7 of the supply and take-up spools 1, 3, and the applied adhesive tape 11 tends to be peeled off because the rotary side shafts 8, 9 are free to rotate.
Problems with the ink ribbon unit 10 fastened by the rubber band 12 as shown in FIG. 4 are that the portion of the ink ribbon 2 which is engaged by the rubber band 12 is caused to wrinkle, and the wrinkles in the ink ribbon 2 are liable to lower the quality of an image printed using the ink ribbon 2.
The packaged ink ribbon unit 10 shown in FIG. 5 is costly because the package bag 13 itself and a process of packaging the ink ribbon unit 10 with the package bag 13 are additionally required.